The invention concerns a method for monitoring bar cutoff in CNC-controlled automatic bar lathes having a main spindle, an auxiliary spindle, and a pull-away carriage.
JP-A 3035902 describes a method with which the cutoff tool or the spindle of the tool machine is protected against damage by removing the cutoff workpiece from the spindle along a predetermined path after completion of the cutting-off procedure.
When carrying-out bar cutoff processes it is necessary to check whether or not the workpiece has been fully severed from the unmachined part. This checking procedure prevents machine damage which could be caused by incompletely severed workpieces.
DE A 36 40 624 describes a diagnostic device with which changes in variable operation parameters at certain typical positions of the machine as well as the reaction times necessary for the changes are stored in a memory during the normal machining (error-free operation) of a workpiece. During the processing of workpieces the changes in variable operation parameters as well as the reaction times are determined in each case at these typical operating positions and compared with values which had been stored during normal processing. In the event that the values do not differ by more than a predetermined amount, the processing is continued.
A process for checking bar cutoff on automatic bar lathes is known in the art through German laid-open publication DE 36 18 349 A1 with which operating conditions are initiated at the end of a predetermined time interval allotted to the cutting-off procedure, which effect a relative rotation of the spindles with respect to each other when the material has been fully severed at the cutoff location. A deviation between the predetermined relative rotation of the main spindle with respect to the auxiliary spindle and the actual relative rotation indicates the existence of a material connection, and a corresponding error signal is issued.
This method has the disadvantage that a separate examination procedure is necessary to monitor the cutting-off procedure, which delays the work process.
It is therefore the purpose of the invention to introduce a method for monitoring bar cutoff which does not introduce a delay in the work process to thereby minimize additional controlling time resulting from monitoring of the cutoff.